public class Main {
    public static void main(String[] args) {
        Solution solution = new Solution();
        solution.mySqrt(4);
    }
}
class Solution {
    public int mySqrt(int x) {
        if (x < 1) return 0;
        long left = 1,right = x;
        while (left<right) {
            long mid = left + (right - left + 1) / 2;
            long ret = mid * mid;
            if (ret<=x) left = mid;
            else if (ret>x) right = mid - 1;
        }
        return (int)left;
    }
}